LONDON — There was no evidence to suggest anyone else was involved in the death of Boris Berezovsky, the self-exiled Russian tycoon who went from Kremlin kingmaker to fiery critic, British police said Sunday.

With an investigation under way, police are treating the death of Berezovsky — who fled to Britain in the early 2000s after a bitter falling out with Russian President Vladimir Putin — as unexplained. But the former oligarch survived assassination attempts and recently faced financial difficulties, prompting speculation as to whether his death was part of a conspiracy — or suicide.

Police said Sunday it would be wrong to speculate on Berezovsky’s cause of death pending the results of an autopsy, but said they had no evidence to suggest anyone else was involved.

“We are at the early stages of the investigation and we are retaining an open mind as we progress,” said Detective Chief Inspector Kevin Brown. “The investigation team is building a picture of the last days of Mr. Berezovsky’s life, speaking to close friends and family to gain a better understanding of his state of mind.”

Police released some details on the circumstances that triggered their investigation into his demise and a subsequent check for hazardous materials at a home he stayed at in Ascot, a town 40 kilometers (25 miles) west of London where Berezovsky’s body was found on Saturday.

A call came into police from the local ambulance service at 3:23 p.m. GMT (11:23 a.m. EDT) Saturday saying a man had been found dead, Thames Valley Police said in a statement on Sunday.

The police said an employee of Berezovsky told how he had called an ambulance after becoming concerned for Berezovsky’s welfare and forced open a bathroom door locked from the inside to find the tycoon’s body on the floor.

The employee was the only person in the house when Berezovsky’s body was discovered, police said. Members of the ex-oligarch’s family arrived at the home while the paramedic was on scene.

After a paramedic declared Berezovsky dead and left the scene, a device measuring the paramedic’s exposure to radiation was triggered, police said. This is why chemical and radiations experts were called to examine the home, they said.

“Officers found nothing of concern in the property and we are now progressing the investigation as normal,” a statement from police said earlier, adding that the majority of the cordon put in place around the property has now been lifted.

Berezovsky — who had survived a number of assassination attempts — amassed a fortune through oil and automobiles during Russia’s chaotic privatization of state assets following the collapse of the Soviet Union in the early 1990s.

Once a member of Russian President Boris Yeltsin’s inner circle, Berezovsky fell out with Yeltsin’s successor, Putin, and fled Britain in the early 2000s to escape fraud charges that he said were politically motivated.

He became a strident and frequent critic of Putin, accusing the leader of ushering in a dictatorship, and accused the security services of organizing 1999 apartment house bombings in Moscow and two other Russian cities that became a pretext for Russian troops to sweep into Chechnya for the second war there in half a decade.

Putin’s spokesman acknowledged Sunday that the Russian president considered Berezovsky an enemy.

“We know for certain that he spared no expense in support of processes, within Russia and beyond, that could be said to have been directed against Russia and Putin,” spokesman Dmitry Peskov said on the independent cable television channel Rain. “He definitely was Putin’s opponent, and unfortunately not only his political opponent, but most likely in other dimensions as well.”

In recent years, Berezovsky fended off legal attacks that often bore political undertones — and others that bit into his fortune.

Russia repeatedly sought to extradite Berezovksy on a wide variety of criminal charges, and the tycoon vehemently rejected allegations over the years that he was linked to several deaths, including that of slain journalist Anna Politkovskaya and ex-KGB agent Alexander Litvinenko.

Berezovsky won a libel case in 2010 against a Kremlin-owned broadcaster that aired a show in which it was suggested he was behind the poisoning of Litvinenko, who had fled Russia with Berezovsky’s help after accusing officials there of plotting to assassinate political opponents.

He took a hit with his divorce from Galina Besharova in 2010, paying what was at the time Britain’s largest divorce settlement. The figure beat a previous record of 48 million pounds ($73.1 million) and was estimated as high as 100 million pounds, though the exact figure was never confirmed.

Last year, Berezovsky lost a multibillion-pound High Court case against fellow Russian Roman Abramovich and was ordered to pay 35 million pounds ($53.3 million) in legal costs.

Berezovsky had claimed that Abramovich, the billionaire owner of Chelsea Football Club, cheated him out of his stakes in the oil group Sibneft, arguing that he blackmailed him into selling the stakes vastly beneath their true worth after he fell from Putin’s good graces.

But a judge threw out the case in August, ruling that Berezovsky was a dishonest and unreliable witness, and rejected Berezovsky’s claims that he was threatened by Putin and Alexander Voloshin, a Putin ally, to coerce him to sell his Sibneft stake.

It also recently emerged that Berezovsky ran up legal bills totaling more than 250,000 pounds in just two months of a case against his former partner, Elena Gorbunova, with whom he had two children and who claimed the businessman owed her millions.

Earlier this week, The Times of London newspaper reported that Berezovsky was selling property — including an Andy Warhol portrait of the former Soviet Union leader Vladimir Lenin — to settle his debts and pay expenses owed to lawyers.

News of Berezovsky’s death has prompted conspiracy theories along with speculation as to his state of mind, given his recent financial setbacks.

Ilya Zhegulev, a journalist with the Russian edition of Forbes magazine, said he spoke with Berezovsky the day before he died and discussed the tycoon’s decision to flee Russia in 2000.

The journalist quoted Berezovsky as saying that during his years in London life had lost meaning.

“I no longer want to be involved in politics,” Zhegulev quoted Berezovsky as saying in a story published Saturday on the Forbes.ru website.

He said Berezovsky told him that he wanted nothing more than to return to Russia. The former oligarch said he had changed his views on Russia, saying he now understood that it should not look to Europe as a model.

“I had absolutely, idealistically imagined that it was possible to build a democratic Russia. And idealistically imagined what democracy was in the center of Europe. I underestimated the inertia of Russia and greatly overestimated the West. This took place gradually. I changed my understanding of Russia’s path,” he quoted Berezovsky as having said.

WASHINGTON – Hillary Clinton challenged Congress on Thursday to combat fake and misleading news on social media, using a post-election appearance to tackle an issue that gripped her presidential campaign and culminated with a shooting incident Sunday in Northwest Washington.